The purpose of this study is to support the Tox21 MOU through the Tox21 Cross-Partner Project (CPP) #2, Cell Line Selection for High Throughput Transcriptomics. Specifically, this project is designed to test the hypothesis that utilizing a certain number of diverse cell lines across a diverse panel of chemicals (e.g., environmental, pharmaceutical, industrial-use) can give resolution to the different classes of compounds and reveal relevant biology for toxicity testing. The first phase of this project was to use existing resources, such as transcriptomics databases, to identify cell lines which maximize biological diversity at the level of gene expression. This in silico analysis is complete and the next step is to verify if the 30 cell lines selected, or a subset of those 30 cell lines, actually capture maximal biological diversity under unperturbed conditions through baseline transcriptome profiling of these cell lines.